U.S. patent number 10,135,513 [Application Number 15/107,372] was granted by the patent office on 2018-11-20 for method and apparatus for reporting channel state information.
This patent grant is currently assigned to LG ELECTRONICS INC.. The grantee listed for this patent is LG ELECTRONICS INC.. Invention is credited to Joonkui Ahn, Bonghoe Kim, Kijun Kim, Jonghyun Park, Dongyoun Seo, Suckchel Yang, Yunjung Yi.
United States Patent |
10,135,513 |
Yi , et al. |
November 20, 2018 |
Method and apparatus for reporting channel state information
Abstract
The method and the apparatus for reporting CSI are provided. The
method comprises receiving reference signal on downlink channel,
selecting CQI corresponding to a channel state based on the
reference signal and transmitting CSI report comprising the
selected CQI, wherein the step of selecting CQI includes selecting
CQI index on a CQI table where the CQI index specifies
modulation.
Inventors: |
Yi; Yunjung (Seoul,
KR), Kim; Kijun (Seoul, KR), Ahn;
Joonkui (Seoul, KR), Kim; Bonghoe (Seoul,
KR), Seo; Dongyoun (Seoul, KR), Yang;
Suckchel (Seoul, KR), Park; Jonghyun (Seoul,
KR) |
Applicant: |
Name |
City |
State |
Country |
Type |
LG ELECTRONICS INC. |
Seoul |
N/A |
KR |
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Assignee: |
LG ELECTRONICS INC. (Seoul,
KR)
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Family
ID: |
53479269 |
Appl.
No.: |
15/107,372 |
Filed: |
December 29, 2014 |
PCT
Filed: |
December 29, 2014 |
PCT No.: |
PCT/KR2014/012987 |
371(c)(1),(2),(4) Date: |
June 22, 2016 |
PCT
Pub. No.: |
WO2015/099515 |
PCT
Pub. Date: |
July 02, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20160337023 A1 |
Nov 17, 2016 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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61948033 |
Mar 5, 2014 |
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61921094 |
Dec 27, 2013 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H04L
1/0026 (20130101); H04B 7/0632 (20130101); H04W
72/0413 (20130101); H04B 7/0626 (20130101); H04L
5/0053 (20130101); H04L 5/0091 (20130101); H04L
5/0046 (20130101); H04L 1/00 (20130101); H04L
1/0016 (20130101); H04L 27/34 (20130101); H04L
5/001 (20130101); H04L 1/0027 (20130101); H04L
1/0029 (20130101) |
Current International
Class: |
H04B
7/06 (20060101); H04L 1/00 (20060101); H04L
27/34 (20060101); H04L 5/00 (20060101); H04W
72/04 (20090101) |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2500254 |
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Sep 2013 |
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GB |
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WO 2013/123961 |
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Aug 2013 |
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WO |
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2013/135475 |
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Sep 2013 |
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WO |
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Other References
Hitachi Ltd., "Further Evaluation and Discussion on 256QAM",
R1-134764, 3GPP TSG-RAN WGI #74b, Guangzhou, China, Oct. 7-11,
2013, 5 pages. cited by applicant .
ZTE, "Consideration on high order modulation for small cell",
R1-130136, 3GPP TSG-RAN WGI Meeting #72, St Julian's, Malta, Jan.
28-Feb. 1, 2013, 6 pages. cited by applicant .
ZTE, "Evaluation and standard impact on EVM and receiver impairment
for small cell 256QAM" , R1-135348, 3GPP TSG RAN WGI Meeting #75,
San Francisco, USA, Nov. 11-15, 2013, 7 pages. cited by
applicant.
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Primary Examiner: Yao; Kwang B
Assistant Examiner: Jeong; Moo Ryong
Attorney, Agent or Firm: Birch, Stewart, Kolasch &
Birch, LLP
Parent Case Text
CROSS REFERENCE TO RELATED APPLICATIONS
This application is the National Phase of PCT International
Application No. PCT/KR2014/012987, filed on Dec. 29, 2014, which
claims priority under 35 U.S.C. 119(e) to U.S. Provisional
Application Nos. 61/921,094, filed on Dec. 27, 2013 and 61/948,033
filed on Mar. 5, 2014, all of which are hereby expressly
incorporated by reference into the present application.
Claims
The invention claimed is:
1. A method for reporting channel state information (CSI) including
channel quality indicator (CQI) by a user equipment, the method
comprising: receiving a reference signal on a downlink channel from
an evolved NodeB (eNB); receiving an indication to use a first CQI
table from the eNB; configuring first CSI comprising a first CQI
index, which is selected on the first CQI table corresponding to a
channel state based on the reference signal; transmitting the first
CSI comprising the first CQI index by using a first physical uplink
control channel (PUCCH) resource to the eNB; receiving an
indication to use a second CQI table via a radio resource control
(RRC) connection reconfiguration message from the eNB; receiving a
configuration indicating whether to transmit or drop CSI during an
RRC reconfiguration period which is initiated by receiving the RRC
connection reconfiguration message from the eNB; when the
configuration indicates to transmit CSI during the RRC
reconfiguration period, during the RRC reconfiguration period:
configuring second CSI comprising a second CQI index, which is only
selected from common entries of the first CQI table and the second
CQI table; and transmitting the second CSI comprising the second
CQI index by using a second PUCCH resource to the eNB, wherein the
second PUCCH resource is an additional different PUCCH resource
than the first PUCCH resource and is used only during the RRC
reconfiguration period, wherein when the configuration indicates to
drop CSI during the RRC reconfiguration period, the second CSI is
not transmitted to the eNB during the RRC reconfiguration period;
and after the RRC reconfiguration period: configuring third CSI
comprising a third CQI index, which is selected on the second CQI
table; and transmitting the third CSI comprising the third CQI
index by using the first PUCCH resource to the eNB.
2. The method of claim 1, wherein the first CQI table is a table
mapping a CQI index into one of quadrature phase-shift keying
(QPSK), 16 quadrature amplitude modulation (QAM) or 64 QAM, wherein
the second CQI table is a table mapping a CQI index into one of
QPSK, 16 QAM, 64 QAM or 256 QAM, and wherein the CQI index for the
first CQI table and the CQI index for the second CQI table are
configured with same bits.
3. The method of claim 2, wherein each of CQI indices 2-4 for the
first CQI table is used for QPSK, and each of CQI indices 2-4 for
the second CQI table is used for 256 QAM.
4. An apparatus for reporting channel state information (CSI)
including a channel quality indicator (CQI), the apparatus
comprising: a radio frequency (RF) unit; and a processor,
operatively coupled to the RF unit, that: controls the RF unit to
receive a reference signal on a downlink channel from an evolved
NodeB (eNB), controls the RF unit to receive an indication to use a
first CQI table from the eNB, configures first CSI comprising a
first CQI index, which is selected on the first CQI table
corresponding to a channel state based on the received reference
signal, controls the RF unit to transmit the first CSI comprising
the first CQI index by using a first physical uplink control
channel (PUCCH) resource to the eNB, controls the RF unit to
receive an indication to use a second CQI table via a radio
resource control (RRC) connection reconfiguration message from the
eNB, controls the RF unit to receive a configuration indicating
whether to transmit or drop CSI during an RRC reconfiguration
period which is initiated by receiving the RRC connection
reconfiguration message from the eNB, when the configuration
indicates to transmit CSI during the RRC reconfiguration period,
during the RRC reconfiguration period: configures second CSI
comprising a second CQI index, which is only selected from common
entries of the first CQI table and the second CQI table, and
controls the RF unit to transmit the second CSI comprising the
second CQI index by using a second PUCCH resource to the eNB,
wherein the second PUCCH resource is an additional different PUCCH
resource than the first PUCCH resource and is used only during the
RRC reconfiguration period, wherein when the configuration
indicates to drop CSI during the RRC reconfiguration period, the
second CSI is not transmitted to the eNB during the RRC
reconfiguration period; and after the RRC reconfiguration period:
configures third CSI comprising a third CQI index, which is
selected on the second CQI table, and controls the RF unit to
transmit the third CSI comprising the third CQI index by using the
first PUCCH resource to the eNB.
5. The apparatus of claim 4, wherein the first CQI table is a table
mapping a CQI index into one of quadrature phase-shift keying
(QPSK), 16 quadrature amplitude modulation (QAM) or 64 QAM, wherein
the second CQI table is a table mapping a CQI index into one of
QPSK, 16 QAM, 64 QAM or 256 QAM, and wherein the CQI index for the
first CQI table and the CQI index for the second CQI table are
configured with same bits.
6. The apparatus of claim 5, wherein each of CQI indices 2-4 for
the first CQI table is used for QPSK, and each of CQI indices 2-4
for the second CQI table is used for 256 QAM.
Description
TECHNICAL FIELD
This technology is related to wireless communication, more
specifically to using modulation of higher order in wireless
communication.
BACKGROUND ART
3rd generation partnership project (3GPP) long term evolution (LTE)
is an improved version of a universal mobile telecommunication
system (UMTS) and a 3GPP release 8. The 3GPP LTE uses orthogonal
frequency division multiple access (OFDMA) in a downlink, and uses
single carrier-frequency division multiple access (SC-FDMA) in an
uplink. The 3GPP LTE employs multiple input multiple output (MIMO)
having up to four antennas. In recent years, there is an ongoing
discussion on 3GPP LTE-advanced (LTE-A) that is an evolution of the
3GPP LTE.
The commercialization of the 3GPP LTE (A) system is being recently
accelerated. The LTE systems are spread more quickly as respond to
users' demand for services that may support higher quality and
higher capacity while ensuring mobility, as well as voice services.
The LTE system provides for low transmission delay, high
transmission rate and system capacity, and enhanced coverage.
Recently standardization for next generation wireless communication
with higher efficiency is in progress.
To handle increasing data traffic, various techniques are being
introduced to enhance transmitting capacity. For example, multiple
input multiple output (MIMO) using multiple antennas, carrier
aggregation (CA) supporting for multiple cells, modulation mode
with higher order, etc. are being considered.
However, the newly introduced techniques need to satisfy backward
compatibility with legacy apparatuses.
SUMMARY OF INVENTION
Technical Problem
An object of the present invention is to provide method and
apparatus for configuring CSI using 256 QAM.
Another object of the present invention is to provide efficient CQI
tables to use 256 QAM.
Yet another object of the present invention is to provide a
structure of CQI tables and CQI indices to use 256 QAM.
Yet another object of the present invention is to provide method
and apparatus for determining CQI tables and selecting CQI index on
the selected CQI table.
Solution to Problem
An embodiment of the present invention is a method for reporting
channel state information (CSI) including channel quality indicator
(CQI) by a user equipment. The method comprises receiving reference
signal on downlink channel, configuring CSI comprising CQI selected
corresponding to a channel state based on the reference signal and
transmitting CSI report on uplink channel, wherein the step of
configuring CSI includes selecting CQI index on a CQI table where
the CQI index specifies modulation.
Another embodiment of the present invention is an apparatus for
reporting CSI including CQI. The apparatus comprises a radio
frequency (RF) unit for transmitting and receiving a radio signal
and a processor operatively coupled to the RF unit, wherein the
processor is configured for transmitting signals via the RF unit
based on a scheduling for UL and/or DL, wherein the RF unit
receives reference signal on downlink channel, and the processor
configures CSI comprising CQI selected corresponding to a channel
stat based on the reference signal, and wherein for configuring
CSI, the processor selects CQI index on a CQI table where the CQI
index specifies modulation.
Advantageous Effects of Invention
According to the present invention, the wireless communication can
be efficiently performed using 256 QAM.
According to the present invention, the UE and the eNB transmits
and receives CQI with optimized amount of information and in an
efficient way in case that they can use 256 QAM.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1 shows a wireless communication system to which the present
invention is applied.
FIG. 2 shows an exemplary concept for a carrier aggregation (CA)
technology according to an exemplary embodiment of the present
invention.
FIG. 3 shows a structure of a radio frame to which the present
invention is applied.
FIG. 4 shows downlink control channels to which the present
invention is applied.
FIG. 5 is a flow chart for describing an operation of UE and eNB
according to the invention(s) in this disclosure.
FIG. 6 is a block diagram which briefly describes a wireless
communication system including a UE and a BS (eNB).
MODE FOR THE INVENTION
FIG. 1 shows a wireless communication system to which the present
invention is applied. The wireless communication system may also be
referred to as an evolved-UMTS terrestrial radio access network
(E-UTRAN) or a long term evolution (LTE)/LTE-A system.
The E-UTRAN includes at least one base station (BS) 20 which
provides a control plane and a user plane to an user equipment (UE)
10. The UE 10 may be fixed or mobile, and may be referred to as
another terminology, such as a mobile station (MS), a user terminal
(UT), a subscriber station (SS), a mobile terminal (MT), a wireless
device, etc. The BS 20 is generally a fixed station that
communicates with the UE 10 and may be referred to as another
terminology, such as an evolved node-B (eNB), a base transceiver
system (BTS), an access point, a cell, node-B, or node etc.
Multi-access schemes applied to the wireless communication system
are not limited. Namely, various multi-access schemes such as CDMA
(Code Division Multiple Access), TDMA (Time Division Multiple
Access), FDMA (Frequency Division Multiple Access), OFDMA
(Orthogonal Frequency Division Multiple Access), SC-FDMA (Single
Carrier-FDMA), OFDM-FDMA, OFDM-TDMA, OFDM-CDMA, or the like, may be
used. For uplink transmission and downlink transmission, a TDD
(Time Division Duplex) scheme in which transmission is made by
using a different time or an FDD (Frequency Division Duplex) scheme
in which transmission is made by using different frequencies may be
used.
The BSs 20 are interconnected by means of an X2 interface. The BSs
20 are also connected by means of an S1 interface to an evolved
packet core (EPC) 30, more specifically, to a mobility management
entity (MME) through S1-MME and to a serving gateway (S-GW) through
S1-U.
The EPC 30 includes an MME, an S-GW, and a packet data
network-gateway (P-GW). The MME has access information of the UE or
capability information of the UE, and such information is generally
used for mobility management of the UE. The S-GW is a gateway
having an E-UTRAN as an end point. The P-GW is a gateway having a
PDN as an end point.
Layers of a radio interface protocol between the UE and the network
can be classified into a first layer (L1), a second layer (L2), and
a third layer (L3) based on the lower three layers of the open
system interconnection (OSI) model that is well-known in the
communication system. Among them, a physical (PHY) layer belonging
to the first layer provides an information transfer service by
using a physical channel, and a radio resource control (RRC) layer
belonging to the third layer serves to control a radio resource
between the UE and the network. For this, the RRC layer exchanges
an RRC message between the UE and the BS.
More details, radio protocol architecture for a user plane
(U-plane) and a control plane (C-plane) are explained. A PHY layer
provides an upper layer with an information transfer service
through a physical channel. The PHY layer is connected to a medium
access control (MAC) layer which is an upper layer of the PHY layer
through a transport channel. Data is transferred between the MAC
layer and the PHY layer through the transport channel. The
transport channel is classified according to how and with what
characteristics data is transferred through a radio interface.
Between different PHY layers, i.e., a PHY layer of a transmitter
and a PHY layer of a receiver, data are transferred through the
physical channel. The physical channel may be modulated using an
orthogonal frequency division multiplexing (OFDM) scheme, and may
utilize time and frequency as a radio resource.
Functions of the MAC layer include mapping between a logical
channel and a transport channel and multiplexing/de-multiplexing on
a transport block provided to a physical channel over a transport
channel of a MAC service data unit (SDU) belonging to the logical
channel. The MAC layer provides a service to a radio link control
(RLC) layer through the logical channel.
Functions of the RLC layer include RLC SDU concatenation,
segmentation, and reassembly. To ensure a variety of quality of
service (QoS) required by a radio bearer (RB), the RLC layer
provides three operation modes, i.e., a transparent mode (TM), an
unacknowledged mode (UM), and an acknowledged mode (AM). The AM RLC
provides error correction by using an automatic repeat request
(ARQ).
Functions of a packet data convergence protocol (PDCP) layer in the
user plane include user data delivery, header compression, and
ciphering. Functions of a PDCP layer in the control plane include
control-plane data delivery and ciphering/integrity protection.
A radio resource control (RRC) layer is defined only in the control
plane. The RRC layer serves to control the logical channel, the
transport channel and the physical channel in association with
configuration, reconfiguration and release of radio bearers (RBs).
An RB is a logical path provided by the first layer (i.e., the PHY
layer) and the second layer (i.e., the MAC layer, the RLC layer,
and the PDCP layer) for data delivery between the UE and the
network.
The setup of the RB implies a process for specifying a radio
protocol layer and channel properties to provide a particular
service and for determining respective detailed parameters and
operations. The RB can be classified into two types, i.e., a
signaling RB (SRB) and a data RB (DRB). The SRB is used as a path
for transmitting an RRC message in the control plane. The DRB is
used as a path for transmitting user data in the user plane.
When an RRC connection is established between an RRC layer of the
UE and an RRC layer of the network, the UE is in an RRC connected
state (it may also be referred to as an RRC connected mode), and
otherwise the UE is in an RRC idle state (it may also be referred
to as an RRC idle mode).
FIG. 2 shows an exemplary concept for a carrier aggregation (CA)
technology according to an exemplary embodiment of the present
invention.
Referring to FIG. 2, the downlink (DL)/uplink (UL) subframe
structure considered in 3GPP LTE-A (LTE-Advanced) system where
multiple CCs are aggregated (in this example, 3 carriers exist) is
illustrated, a UE can monitor and receive DL signal/data from
multiple DL CCs at the same time. However, even if a cell is
managing N DL CCs, the network may configure a UE with M DL CCs,
where M.ltoreq.N so that the UE's monitoring of the DL signal/data
is limited to those M DL CCs. In addition, the network may
configure L DL CCs as the main DL CCs from which the UE should
monitor/receive DL signal/data with a priority, either
UE-specifically or cell-specifically, where L.ltoreq.M.ltoreq.N. So
the UE may support one or more carriers (Carrier 1 or more Carriers
2 . . . N) according to UE's capability thereof.
A Carrier or a cell may be divided into a primary component carrier
(PCC) and a secondary component carrier (SCC) depending on whether
or not they are activated. A PCC is always activated, and an SCC is
activated or deactivated according to particular conditions. That
is, a PCell (primary serving cell) is a resource in which the UE
initially establishes a connection (or a RRC connection) among
several serving cells. The PCell serves as a connection (or RRC
connection) for signaling with respect to a plurality of cells
(CCs), and is a special CC for managing UE context which is
connection information related to the UE. Further, when the PCell
(PCC) establishes the connection with the UE and thus is in an RRC
connected mode, the PCC always exists in an activation state. A
SCell (secondary serving cell) is a resource assigned to the UE
other than the PCell (PCC). The SCell is an extended carrier for
additional resource assignment, etc., in addition to the PCC, and
can be divided into an activation state and a deactivation state.
The SCell is initially in the deactivation state. If the SCell is
deactivated, it includes not transmit sounding reference signal
(SRS) on the SCell, not report CQI/PMI/RI/PTI for the SCell, not
transmit on UL-SCH on the SCell, not monitor the PDCCH on the
SCell, not monitor the PDCCH for the SCell. The UE receives an
Activation/Deactivation MAC control element in this TI activating
or deactivating the SCell.
To enhance the user throughput, it is also considered to allow
inter-node resource aggregation over more than one eNB/node where a
UE may be configured with more than one carrier groups. It is
configured PCell per each carrier group which particularly may not
be deactivated. In other words, PCell per each carrier group may
maintain its state to active all the time once it is configured to
a UE. In that case, serving cell index i corresponding to a PCell
in a carrier group which does not include serving cell index 0
which is a master PCell cannot be used for
activation/deactivation.
More particularly, if serving cell index 0, 1, 2 are configured by
one carrier group whereas serving cell index 3, 4, 5 are configured
by the other carrier group in two carrier group scenarios where
serving cell index 0 is PCell and serving cell index 3 is the PCell
of the second carrier group, then only bits corresponding 1 and 2
are assumed to be valid for the first carrier group cell
activation/deactivation messages whereas bits corresponding 4 and 5
are assumed to be valid for the second carrier group cell
activation/deactivation. To make some distinction between PCell for
the first carrier group and the second carrier group, the PCell for
the second carrier group can be noted as S-PCell hereinafter.
Herein, the index of the serving cell may be a logical index
determined relatively for each UE, or may be a physical index for
indicating a cell of a specific frequency band. The CA system
supports a non-cross carrier scheduling of self-carrier scheduling,
or cross carrier scheduling.
FIG. 3 shows a structure of a radio frame to which the present
invention is applied.
Referring to FIG. 3, a radio frame includes 10 subframes, and one
subframe includes two slots. The time taken for one subframe to be
transmitted is called a Transmission Time Interval (TI). For
example, the length of one subframe may be 1 ms, and the length of
one slot may be 0.5 ms.
One slot includes a plurality of OFDM symbols in the time domain
and includes a plurality of Resource Blocks (RBs) in the frequency
domain. An OFDM symbol is for representing one symbol period
because downlink OFDMA is used in 3GPP LTE system and it may be
called an SC-FDMA symbol or a symbol period depending on a
multi-access scheme. An RB is a resource allocation unit, and it
includes a plurality of contiguous subcarriers in one slot. The
number of OFDM symbols included in one slot may vary according to
the configuration of the CP (Cyclic Prefix). The CP includes an
extended CP and a normal CP. For example, if normal CP case, the
OFDM symbol is composed by 7. If configured by the extended CP, it
includes 6 OFDM symbols in one slot. If the channel status is
unstable such as moving at a fast pace UE, the extended CP can be
configured to reduce an inter-symbol interference. Herein, the
structure of the radio frame is only illustrative, and the number
of subframes included in a radio frame, or the number of slots
included in a subframe, and the number of OFDM symbols included in
a slot may be changed in various ways to apply new communication
system. This invention has no limitation to adapt to other system
by varying the specific feature and the embodiment of the invention
can apply with changeable manners to a corresponding system.
The downlink slot includes a plurality of OFDM symbols in the time
domain. For example, one downlink slot is illustrated as including
7 OFDMA symbols and one Resource Block (RB) is illustrated as
including 12 subcarriers in the frequency domain, but not limited
thereto. Each element on the resource grid is called a Resource
Element (RE). One resource block includes 12.times.7 (or 6) REs.
The number N.sup.DL of resource blocks included in a downlink slot
depends on a downlink transmission bandwidth that is set in a cell.
Bandwidths that are taken into account in LTE are 1.4 MHz, 3 MHz, 5
MHz, 10 MHz, 15 MHz, and 20 MHz. If the bandwidths are represented
by the number of resource blocks, they are 6, 15, 25, 50, 75, and
100, respectively.
The former 0 or 1 or 2 or 3 OFDM symbols of the first slot within
the subframe correspond to a control region to be assigned with a
control channel, and the remaining OFDM symbols thereof become a
data region to which a physical downlink shared chancel (PDSCH) is
allocated. Examples of downlink control channels include a Physical
Control Format Indicator Channel (PCFICH), a Physical Downlink
Control Channel (PDCCH), and a Physical Hybrid-ARQ Indicator
Channel (PHICH).
The PCFICH transmitted in a 1st OFDM symbol of the subframe carries
a control format indicator (CFI) regarding the number of OFDM
symbols (i.e., a size of the control region) used for transmission
of control channels in the subframe, that is, carries information
regarding the number of OFDM symbols used for transmission of
control channels within the subframe. The UE first receives the CFI
on the PCFICH, and thereafter monitors the PDCCH.
The PHICH carries acknowledgement (ACK)/not-acknowledgement (NACK)
signals in response to an uplink Hybrid Automatic Repeat Request
(HARQ). That is, ACK/NACK signals for uplink data that has been
transmitted by a UE are transmitted on a PHICH.
A PDCCH (or ePDCCH) is a downlink physical channel, a PDCCH can
carry information about the resource allocation and transmission
format of a Downlink Shared Channel (DL-SCH), information about the
resource allocation of an Uplink Shared Channel (UL-SCH), paging
information about a Paging Channel (PCH), system information on a
DL-SCH, information about the resource allocation of a higher layer
control message, such as a random access response transmitted on a
PDSCH, a set of transmit power control commands for UEs within a
certain UE group, the activation of a Voice over Internet Protocol
(VoIP), etc.
A plurality of PDCCHs may be transmitted within the control region,
and a UE can monitor a plurality of PDCCHs. The PDCCH is
transmitted on one Control Channel Element (CCE) or on an
aggregation of some contiguous CCEs. A CCE is a logical assignment
unit for providing a coding rate according to the state of a radio
channel to a PDCCH. The CCE corresponds to a plurality of resource
element groups (REGs). A format of the PDCCH and the number of bits
of the available PDCCH are determined according to a correlation
between the number of CCEs and the coding rate provided by the
CCEs.
The wireless communication system of the present invention uses
blind decoding for Physical Downlink Control Channel (PDCCH)
detection. The blind decoding is a scheme in which a desired
identifier is de-masked from a CRC of a PDCCH to determine whether
the PDCCH is its own channel by performing CRC error checking. An
eNB determines a PDCCH format according to a Downlink Control
Information (DCI) to be transmitted to a UE. Thereafter, the eNB
attaches a cyclic redundancy check (CRC) to the DCI, and masks a
unique identifier (referred to as a radio network temporary
identifier (RNTI)) to the CRC according to an owner or usage of the
PDCCH. For example, if the PDCCH is for a specific UE, a unique
identifier (e.g., cell-RNTI (C-RNTI)) of the UE may be masked to
the CRC. Alternatively, if the PDCCH is for a paging message, a
paging indicator identifier (e.g., paging-RNTI (e.g., P-RNTI)) may
be masked to the CRC. If the PDCCH is for system information (more
specifically, a system information block (SIB) to be described
below), a system information identifier and system information RNTI
(e.g., SI-RNTI) may be masked to the CRC. To indicate a random
access response that is a response for transmission of a random
access preamble of the UE, a random access-RNTI (e.g., RA-RNTI) may
be masked to the CRC.
Thus, the BS determines a PDCCH format according to a Downlink
Control Information (DCI) to be transmitted to the UE, and attaches
a cyclic redundancy check (CRC) to control information. The DCI
includes uplink or downlink scheduling information or includes an
uplink transmit (Tx) power control command for arbitrary UE groups.
The DCI is differently used depending on its format, and it also
has a different field that is defined within the DCI.
Meanwhile, an uplink subframe may be divided into a control region
to which a physical uplink control channel (PUCCH) that carries
uplink control information is allocated; the control information
includes an ACK/NACK response of downlink transmission. A data
region to which physical uplink shared channel (PUSCH) that carries
user data is allocated in the frequency domain.
The PUCCH may support multiple formats. Namely, it can transmit
uplink control information having different number of bits per
subframe according to a modulation scheme. PUCCH format 1 is used
to transmit a scheduling request (SR), and PUCCH formats 1a and 1b
are used to transmit an HARQ ACK/NACK signal. PUCCH format 2 is
used to transmit a channel quality indication (CQI), and PUCCH
formats 2a and 2b are used to transmit a CQI and a HARQ ACK/NACK.
When an HARQ ACK/NACK is transmitted alone, PUCCH formats 1a and 1b
are used, and when an SR is transmitted alone, PUCCH format 1 is
used. And PUCCH format 3 may be used for the TDD system, and also
the FDD system.
Herein, an ePDCCH can be one of solutions of limitation for a PDCCH
transmission or new control information transmission of near future
communication system including a new type of carrier as shown in
FIG. 4.
FIG. 4 shows downlink control channels to which the present
invention is applied. The ePDCCH which can be multiplexed with the
PDSCH can support multiple Scells of the CA.
Referring to FIG. 4, the UE can monitor a plurality of
PDCCH/ePDCCHs within the control region and/or data region. While
EPDCCH is transmitted in UE specific search space, PDCCH can be
transmitted in common search space as well as in UE specific search
space. As the PDCCH is transmitted on CCE, ePDCCH can be
transmitted on eCCE (enhanced CCE) as an aggregation of some
contiguous CCEs, the eCCE corresponds to a plurality of REGs. If
ePDCCH is more efficient than PDCCH, it is worthwhile to have
subframes where only ePDCCHs are used without PDCCHs. The PDCCHs
and new ePDCCH only subframes, or have only ePDCCH only subframes
can be in a new type of carrier as NC which has both legacy LTE
subframes. It is still assumed that MBSFN subframes exist in a new
carrier NC. Whether to use PDCCH in multimedia broadcast single
frequency network (MBSFN) subframes in NC and how many ODFM symbols
will be allocated if used can be configured via RRC signaling.
Further TM10 and new TM mode of UE can be considered for new
carrier type as well. Hereafter, new carrier type refers to a
carrier where all or part of legacy signals can be omitted or
transmitted in different manners. For example, a new carrier may
refer a carrier where a cell-specific common reference signal (CRS)
may be omitted in some subframes or physical broadcast channel
(PBCH) may not be transmitted.
To support downlink scheduling, a UE may provide report on channel
state to the eNB. This report can be called as channel state
information (CSI). CSI may indicate instantaneous downlink channel
quality in both the time and frequency domains. The UE may obtain
channel state information by measuring on reference signals
transmitted in the downlink.
Based on the CSI, the eNB can perform downlink scheduling i.e.
assign resources for downlink transmission to different UEs.
CSI may contain channel quality indicator (CQI), precoding matrix
indicator (PMI), rank indicator (RI), etc.
The UE may use downlink reference signal when the UE perform
measurement for CSI. The downlink reference signals are predefined
signals which occupies specific resource elements in the downlink
time-frequency grid. As downlink reference signals, there are cell
specific reference signals (CRS), demodulation reference signal
(DM-RS), CSI reference signal (CSI-RS), MBSFN reference signals,
positioning reference signals, etc.
CRS may be used for channel estimation for coherent demodulation
and also can be used for acquiring channel state information. In
addition, CSI-RS is specifically intended to be used for obtaining
channel state information.
As to CSI-RS, 3GPP TS 36.211 V11.2.0 (2013-02) can be referred.
Multiple CSI reference signal configurations can be used in a given
cell. A UE can be configured with multiple sets of CSI reference
signals, for example, up to three configurations for which the UE
shall assume non-zero transmission power for the CSI-RS and, for
another example, zero or more configurations for which the UE shall
assume zero transmission power.
The CSI-RS configurations for which the UE shall assume non-zero
transmission power are provided by higher layers.
The CSI-RS configurations for which the UE shall assume zero
transmission power in a subframe are given by a bitmap. For each
bit set to one in the 16-bit bitmap, the UE shall assume zero
transmission power for the resource elements corresponding to the
four CSI reference signal column in Tables 6.10.5.2-1 and
6.10.5.2-2 of 3GPP TS 36.211 V11.2.0 for normal and extended cyclic
prefix, respectively, except for resource elements that overlap
with those for which the UE shall assume non-zero transmission
power CSI-RS as configured by higher layers. The most significant
bit corresponds to the lowest CSI reference signal configuration
index and subsequent bits in the bitmap correspond to
configurations with indices in increasing order.
CSI reference signals can only occur in downlink slots where
n.sub.s mod 2 fulfils the condition in Tables 6.10.5.2-1 and
6.10.5.2-2 of 3GPP TS 36.211 V11.2.0 for normal and extended cyclic
prefix, respectively, and where the subframe number fulfils the
conditions in Section 6.10.5.3 3GPP TS 36.211 V11.2.0.
The UE may assume that CSI reference signals are not transmitted in
the special subframe(s) in case of frame structure type 2, in
subframes where transmission of a CSI-RS would collide with
transmission of synchronization signals, PBCH, or
System-InformationBlockType1 messages, and in the primary cell in
subframes configured for transmission of paging messages in the
primary cell for any UE with the cell-specific paging
configuration.
The time and frequency resources that can be used by the UE to
report CSI which consists of channel quality indicator (CQI),
precoding matrix indicator (PMI), precoding type indicator (PTI),
and/or rank indication (RI) are controlled by the eNB. For spatial
multiplexing, the UE may determine a RI corresponding to the number
of useful transmission layers.
A UE in transmission mode 8 or 9 is configured with or without
PMI/RI reporting by the higher layer parameter pmi-R-Report.
A UE in transmission mode 10 can be configured with one or more CSI
processes per serving cell by higher layers. Each CSI process is
associated with a CSI-RS resource (defined in Section 7.2.5 of 3GPP
TS 36.211 V11.2.0) and a CSI-interference measurement (CSI-IM)
resource (defined in Section 7.2.6 of 3GPP TS 36.211 V11.2.0). A
CSI reported by the UE corresponds to a CSI process configured by
higher layers. Each CSI process can be configured with or without
PMI/RI reporting by higher layer signalling.
A UE is configured with resource-restricted CSI measurements if the
subframe sets C.sub.CSI,0 and C.sub.CSI,1 are configured by higher
layers.
CSI reporting is periodic or aperiodic.
If the UE is configured with more than one serving cell, it
transmits CSI for activated serving cell(s) only.
If a UE is not configured for simultaneous PUSCH and PUCCH
transmission, it shall transmit periodic CSI reporting on PUCCH as
defined hereafter in subframes with no PUSCH allocation.
If a UE is not configured for simultaneous PUSCH and PUCCH
transmission, it shall transmit periodic CSI reporting on PUSCH of
the serving cell with smallest ServCellIndex as defined hereafter
in subframes with a PUSCH allocation, where the UE shall use the
same PUCCH-based periodic CSI reporting format on PUSCH.
A UE shall transmit aperiodic CSI reporting on PUSCH if the
conditions specified hereafter are met. For aperiodic CQI/PMI
reporting, RI reporting is transmitted only if the configured CSI
feedback type supports RI reporting.
For serving cell c, a UE configured in transmission mode 10 with
PMI/RI reporting for a CSI process can be configured with a
`RI-reference CSI process`. If the UE is configured with a
`RI-reference CSI process` for the CSI process, the reported RI for
the CSI process shall be the same as the reported RI for the
configured `RI-reference CSI process`. The UE is not expected to
receive an aperiodic CSI report request for a given subframe
triggering a CSI report including CSI associated with the CSI
process and not including CSI associated with the configured
`RI-reference CSI process`.
For a UE in transmission mode 10, in case of collision between CSI
reports of same serving cell with PUCCH reporting type of the same
priority, and the CSI reports corresponding to different CSI
processes, the CSI reports corresponding to all CSI processes
except the CSI process with the lowest CSIProcessIndex are
dropped.
If the UE is configured with more than one serving cell, the UE
transmits a CSI report of only one serving cell in any given
subframe. For a given subframe, in case of collision of a CSI
report with PUCCH reporting type 3, 5, 6, or 2a of one serving cell
with a CSI report with PUCCH reporting type 1, 1a, 2, 2b, 2c, or 4
of another serving cell, the latter CSI with PUCCH reporting type
(1, 1a, 2, 2b, 2c, or 4) has lower priority and is dropped. For a
given subframe, in case of collision of CSI report with PUCCH
reporting type 2, 2b, 2c, or 4 of one serving cell with CSI report
with PUCCH reporting type 1 or 1 a of another serving cell, the
latter CSI report with PUCCH reporting type 1, or 1a has lower
priority and is dropped.
For a given subframe and UE in transmission mode 1-9, in case of
collision between CSI reports of different serving cells with PUCCH
reporting type of the same priority, the CSI of the serving cell
with lowest ServCellIndex is reported, and CSI of all other serving
cells are dropped.
For a given subframe and UE in transmission mode 10, in case of
collision between CSI reports of different serving cells with PUCCH
reporting type of the same priority and the CSI reports
corresponding to CSI processes with same CSIProcessIndex, the CSI
reports of all serving cells except the serving cell with lowest
ServCellIndex are dropped.
For a given subframe and UE in transmission mode 10, in case of
collision between CSI reports of different serving cells with PUCCH
reporting type of the same priority and the CSI reports
corresponding to CSI processes with different CSIProcessIndex, the
CSI reports of all serving cells except the serving cell with CSI
reports corresponding to CSI process with the lowest
CSIProcessIndex are dropped.
As described above, CSI report may contain CQI.
The CQI indices and their interpretations are given in Table 1.
Table 1 is a table for 4-bit CQI.
TABLE-US-00001 TABLE 1 CQI index modulation code rate .times. 1024
efficiency 0 out of range 1 QPSK 78 0.1523 2 QPSK 120 0.2344 3 QPSK
193 0.3770 4 QPSK 308 0.6016 5 QPSK 449 0.8770 6 QPSK 602 1.1758 7
16QAM 378 1.4766 8 16QAM 490 1.9141 9 16QAM 616 2.4063 10 64QAM 466
2.7305 11 64QAM 567 3.3223 12 64QAM 666 3.9023 13 64QAM 772 4.5234
14 64QAM 873 5.1152 15 64QAM 948 5.5547
Based on an unrestricted observation interval in time and
frequency, the UE shall derive for each CQI value reported in
uplink subframe n the highest CQI index between 1 and 15 in Table 1
which satisfies the following condition, or CQI index 0 if CQI
index 1 does not satisfy the condition: A single PDSCH transport
block with a combination of modulation scheme and transport block
size corresponding to the CQI index, and occupying a group of
downlink physical resource blocks termed the CSI reference
resource, could be received with a transport block error
probability not exceeding 0.1.
If CSI subframe sets C.sub.CSI,0 and C.sub.CSI,1 are configured by
higher layers, each CSI reference resource belongs to either
C.sub.CSI,0 or C.sub.CSI,1 but not to both. When CSI subframe sets
C.sub.CSI,0 and C.sub.CSI,1 are configured by higher layers a UE is
not expected to receive a trigger for which the CSI reference
resource is in subframe that does not belong to either subframe
set. For a UE in transmission mode 10 and periodic CSI reporting,
the CSI subframe set for the CSI reference resource is configured
by higher layers for each CSI process.
For a UE in transmission mode 9 when parameter pmi-RI-Report is
configured by higher layers, the UE shall derive the channel
measurements for computing the CQI value reported in uplink
subframe n based on only the Channel-State Information (CSI)
reference signals (CSI-RS) defined in 3GPP TS 36.211 V11.2.0 for
which the UE is configured to assume non-zero power for the CSI-RS.
For a UE in transmission mode 9 when the parameter pmi-R-Report is
not configured by higher layers or in other transmission modes the
UE shall derive the channel measurements for computing CQI based on
CRS.
For a UE in transmission mode 10, the UE shall derive the channel
measurements for computing the CQI value reported in uplink
subframe n and corresponding to a CSI process, based on only the
non-zero power CSI-RS within a configured CSI-RS resource
associated with the CSI process.
For a UE in transmission mode 10, the UE shall derive the
interference measurements for computing the CQI value reported in
uplink subframe n and corresponding to a CSI process, based on only
the zero power CSI-RS within the configured CSI-IM resource
associated with the CSI process. If the UE in transmission mode 10
is configured by higher layers for CSI subframe sets C.sub.CSI,0
and C.sub.CSI,1, the configured CSI-IM resource within the subframe
subset belonging to the CSI reference resource is used to derive
the interference measurement.
A combination of modulation scheme and transport block size
corresponds to a CQI index if: the combination could be signalled
for transmission on the PDSCH in the CSI reference resource
according to the relevant Transport Block Size table, and the
modulation scheme is indicated by the CQI index, and the
combination of transport block size and modulation scheme when
applied to the reference resource results in the effective channel
code rate which is the closest possible to the code rate indicated
by the CQI index. If more than one combination of transport block
size and modulation scheme results in an effective channel code
rate equally close to the code rate indicated by the CQI index,
only the combination with the smallest of such transport block
sizes is relevant.
The CSI reference resource for a serving cell is defined as
follows: In the frequency domain, the CSI reference resource is
defined by the group of downlink physical resource blocks
corresponding to the band to which the derived CQI value relates.
In the time domain, (1) for a UE configured in transmission mode
1-9 or transmission mode 10 with a single configured CSI process
for the serving cell, the CSI reference resource is defined by a
single downlink subframe n-n.sub.CQI.sub._.sub.ref, where for
periodic CSI reporting n.sub.CQI.sub._.sub.ref is the smallest
value greater than or equal to 4, such that it corresponds to a
valid downlink subframe; where for aperiodic CSI reporting
n.sub.CQI.sub._.sub.ref is such that the reference resource is in
the same valid downlink subframe as the corresponding CSI request
in an uplink DCI format; where for aperiodic CSI reporting
n.sub.CQI.sub._.sub.ref is equal to 4 and downlink subframe
n-n.sub.CQI.sub._.sub.ref of corresponds to a valid downlink
subframe, where downlink subframe n-n.sub.CQI.sub._.sub.ref is
received after the subframe with the corresponding CSI request in a
Random Access Response Grant, (2) for a UE configured in
transmission mode 10 with multiple configured CSI processes for the
serving cell, the CSI reference resource for a given CSI process is
defined by a single downlink subframe n-n.sub.CQI.sub._.sub.ref,
where for FDD and periodic or aperiodic CSI reporting
n.sub.CQI.sub._.sub.ref is the smallest value greater than or equal
to 5, such that it corresponds to a valid downlink subframe; where
for FDD and aperiodic CSI reporting n.sub.CQI.sub._.sub.ref is
equal to 5 and downlink subframe n-n.sub.CQI.sub._.sub.ref
corresponds to a valid downlink subframe, where downlink subframe
n-n.sub.CQI.sub._.sub.ref is received after the subframe with the
corresponding CSI request in a Random Access Response Grant.
A downlink subframe in a serving cell shall be considered to be
valid if: it is configured as a downlink subframe for that UE, and
except for transmission mode 9 or 10, it is not an MBSFN subframe,
and it does not contain a DwPTS field in case the length of DwPTS
is 7680T.sub.s, and less, and it does not fall within a configured
measurement gap for that UE, and for periodic CSI reporting, it is
an element of the CSI subframe set linked to the periodic CSI
report when that UE is configured with CSI subframe sets.
If there is no valid downlink subframe for the CSI reference
resource in a serving cell, CSI reporting is omitted for the
serving cell in uplink subframe n.
In the layer domain, the CSI reference resource is defined by any
RI and PMI on which the CQI is conditioned.
In the CSI reference resource, the UE shall assume the following
for the purpose of deriving the CQI index, and if also configured,
PMI and RI:
(i) The first 3 OFDM symbols are occupied by control signaling.
(ii) No resource elements used by primary or secondary
synchronisation signals or PBCH.
(iii) CP length of the non-MBSFN subframes
(iv) Redundancy Version 0
(v) If CSI-RS is used for channel measurements, the ratio of PDSCH
EPRE to CSI-RS EPRE is as given in Section 7.2.5 of 3GPP TS 36.211
V11.2.0
(vi) For transmission mode 9 CSI reporting: {circle around (1)} CRS
REs are as in non-MBSFN subframes. {circle around (2)} If the UE is
configured for PMI/RI reporting, the UE-specific reference signal
overhead is consistent with the most recent reported rank; and
PDSCH signals on antenna ports {7 . . . 6+v} for v layers would
result in signals equivalent to corresponding symbols transmitted
on antenna ports {15 . . . 14+P}, as given by
.function..function..function..function..function..upsilon..times..functi-
on. ##EQU00001## where x(i)=[x.sup.(0)(i) . . .
x.sup.(v-1)(i)].sup.T is a vector of symbols from the layer mapping
in section 6.3.3.2 of 3GPP TS 36.211 V11.2.0, P.di-elect cons.{1,
2, 4, 8} is the number of CSI-RS ports configured, and if only one
CSI-RS port is configured, W(i) is 1 and the UE-specific reference
signal overhead is 12 REs; if more than one CSI-RS ports are
configured, W(i) is the precoding matrix corresponding to the
reported PMI applicable to x(i). The corresponding PDSCH signals
transmitted on antenna ports {15 . . . 14+P} would have a ratio of
EPRE to CSI-RS EPRE equal to the ratio given in section 7.2.5 of
3GPP TS 36.211 V11.2.0.
For transmission mode 10 CSI reporting, if a CSI process is
configured without PMI/RI reporting: (1) If the number of antenna
ports of the associated CSI-RS resource is one, a PDSCH
transmission is on single-antenna port, port 7. The channel on
antenna port {7} is inferred from the channel on antenna port {15}
of the associated CSI-RS resource. {circle around (1)} CRS REs are
as in non-MBSFN subframes. {circle around (2)} The UE-specific
reference signal overhead is 12 REs per PRB pair. (2) Otherwise,
{circle around (1)} If the number of antenna ports of the
associated CSI-RS resource is 2, the PDSCH transmission scheme
assumes the transmit diversity scheme defined in section 7.1.2 on
antenna ports {0,1} except that the channels on antenna ports {0,1}
are inferred from the channels on antenna port {15, 16} of the
associated CSI resource respectively. {circle around (2)} If the
number of antenna ports of the associated CSI-RS resource is 4, the
PDSCH transmission scheme assumes the transmit diversity scheme
defined in section 7.1.2 on antenna ports {0, 1, 2, 3} except that
the channels on antenna ports {0, 1, 2, 3} are inferred from the
channels on antenna ports {15, 16, 17, 18} of the associated CSI-RS
resource respectively. {circle around (3)} The UE is not expected
to be configured with more than 4 antenna ports for the CSI-RS
resource associated with the CSI process configured without PMI/RI
reporting. {circle around (4)} The overhead of CRS REs is assuming
the same number of antenna ports as that of the associated CSI-RS
resource. {circle around (5)} UE-specific reference signal overhead
is zero.
For transmission mode 10 CSI reporting, if a CSI process is
configured with PMI/RI reporting: (1) CRS REs are as in non-MBSFN
subframes. (2) The UE-specific reference signal overhead is
consistent with the most recent reported rank; and PDSCH signals on
antenna ports {7 . . . 6+v} for v layers would result in signals
equivalent to corresponding symbols transmitted on antenna ports
{15 . . . 14+P}, as given by
.function..function..function..function..function..upsilon..times..functi-
on. ##EQU00002## where x(i)=[x.sup.(0)(i) . . .
x.sup.(v-1)(i)].sup.T is a vector of symbols from the layer mapping
in section 6.3.3.2 of 3GPP TS 36.211 V11.2.0, P.di-elect cons.{1,
2, 4, 8} is the number of antenna ports of the associated CSI-RS
resource, and if P=1, W(i) is 1 and the UE-specific reference
signal overhead is 12REs; if P>1, W(i) is the precoding matrix
corresponding to the reported PMI applicable to x(i). The
corresponding PDSCH signals transmitted on antenna ports {15 . . .
14+P} would have a ratio of EPRE to CSI-RS EPRE equal to the ratio
given in section 7.2.5 of 3GPP TS 36.211 V11.2.0.
It is assumed that no REs is allocated for CSI-RS and zero-power
CSI-RS and no REs is allocated for PRS.
The PDSCH transmission scheme given by Table 2 depending on the
transmission mode currently configured for the UE (which may be the
default mode).
TABLE-US-00002 TABLE 2 Trans- mission mode Transmission scheme of
PDSCH 1 Single-antenna port, port 0 2 Transmit diversity 3 Transmit
diversity if the associated rank indicator is 1, otherwise large
delay CDD 4 Closed-loop spatial multiplexing 5 Multi-user MIMO 6
Closed-loop spatial multiplexing with a single transmission layer 7
If the number of PBCH antenna ports is one, Single-antenna port,
port 0; otherwise Transmit diversity 8 If the UE is configured
without PMI/RI reporting: if the number of PBCH antenna ports is
one, single-antenna port, port 0; otherwise transmit diversity If
the UE is configured with PMI/RI reporting: closed-loop spatial
multiplexing 9 If the UE is configured without PMI/RI reporting: if
the number of PBCH antenna ports is one, single-antenna port, port
0; otherwise transmit diversity If the UE is configured with PMI/RI
reporting: if the number of CSI-RS ports is one, single-antenna
port, port 7; otherwise up to 8 layer transmission, ports 7-14 (see
subclause 7.1.5B) 10 If a CSI process of the UE is configured
without PMI/RI reporting: if the number of CSI-RS ports is one,
single- antenna port, port7; otherwise transmit diversity If a CSI
process of the UE is configured with PMI/RI reporting: if the
number of CSI-RS ports is one, single- antenna port, port 7;
otherwise up to 8 layer transmission, ports 7-14 (see subclause
7.1.5B)
If CRS is used for channel measurements, the ratio of PDSCH EPRE to
cell-specific RS EPRE is as given in Section 5.2 of 3GPP TS 36.211
V11.2.0 with the exception of .rho..sub.A which shall be assumed to
be (i) .rho..sub.A=P.sub.A+.DELTA..sub.offset+10 log.sub.10(2) [dB]
for any modulation scheme, if the UE is configured with
transmission mode 2 with 4 cell-specific antenna ports, or
transmission mode 3 with 4 cell-specific antenna ports and the
associated RI is equal to one; (ii)
.rho..sub.A=P.sub.A+.DELTA..sub.offset [dB] for any modulation
scheme and any number of layers, otherwise.
The shift .DELTA..sub.offset is given by the parameter
nomPDSCH-RS-EPRE-Offset which is configured by higher-layer
signalling.
Meanwhile, in LTE-Advanced, to improve spectral efficiency, higher
order modulation such as 256 QAM is considered. Up to LTE Rel-11,
only QPSK, 16 QAM and 64 QAM were supported. Thus, necessary
changes needs to support higher order modulation such as 256
QAM.
In this disclosure, it is more specifically described how to
perform CQI feedback when a UE supports 256 QAM where CQI table for
256 QAM may be different from the legacy table which support only
QPSK, 16 QAM and 64 QAM.
More specifically, an example of two different tables as below is
described. Table 3 is 4 bit CQI table for legacy i.e. non-256 QAM
enabled and Table 4 is 4 bit CQI table for 256 QAM.
TABLE-US-00003 TABLE 3 CQI index modulation code rate .times. 1024
efficiency 0 out of range 1 QPSK 78 0.1523 2 QPSK 120 0.2344 3 QPSK
193 0.3770 4 QPSK 308 0.6016 5 QPSK 449 0.8770 6 QPSK 602 1.1758 7
16QAM 378 1.4766 8 16QAM 490 1.9141 9 16QAM 616 2.4063 10 64QAM 466
2.7305 11 64QAM 567 3.3223 12 64QAM 666 3.9023 13 64QAM 772 4.5234
14 64QAM 873 5.1152 15 64QAM 948 5.5547
TABLE-US-00004 TABLE 4 CQI index modulation code rate .times. 1024
efficiency 0 out of range 1 QPSK 78 0.1523 2 QPSK 449 0.8770 3 QPSK
602 1.1758 4 16QAM 378 1.4766 5 16QAM 490 1.9141 6 16QAM 616 2.4063
7 64QAM 466 2.7305 8 64QAM 567 3.3223 9 64QAM 666 3.9023 10 64QAM
772 4.5234 11 64QAM 873 5.1152 12 64QAM 948 5.5547 13 256QAM xxx
x.xxxx 14 256QAM xxx x.xxxx 15 256QAM xxx x.xxxx
Since the operating signal-to-interference-and-noise ratio (SINR)
range for each modulation is different, depending on operating SINR
range of a UE, it may be better to use legacy table or 256 QAM
table. As operating SINR range can change dynamically, a mechanism
to switch between two tables for CQI optimization can be
considered.
Firstly, a mechanism to semi-statically change the table can be
considered. In terms of configuration, the following options
(I).about.(III) can be considered.
(I) CQI table is determined when modulation and coding scheme (MCS)
table is configured. For example, a UE is configured (implicitly)
to use 256 QAM CQI table when a UE is configured to use 256 QAM MCS
table for its modulation and transport block size (TBS)
calculation. Using this option, CQI table which can fall back to
legacy table could be used only when MCS table is changed to legacy
table from 256 QAM table. In other words, downlink modulation
configuration will determine feedback table implicitly.
(II) CQI table is determined independently on the MCS table. In
this case, either a separate configuration or indication to which
table used for 256 QAM can be given to a UE independently from the
MCS table. Regardless of actual usage of 256 QAM in downlink,
uplink feedback can be configured separately to use a table for the
feedback. This option may be to configure different table per
measurement subframe set or per subframe set or per ICIC subframe
set.
(III) Hybrid of (I) and (II) can be considered as well where a UE
may assume to use 256 QAM table unless it is configured to use
another table when downlink 256 QAM is configured. Or, the opposite
configuration (by default, a UE uses legacy table unless explicit
configuration to use 256 QAM table is configured) is also feasible.
For example, in this case, regardless of CQI table configuration,
whether to use 256 QAM MCS/TBS table or not may be dependent on
subframe or DCI format or other dynamic signaling. For example, DCI
1A uses legacy table whereas other DCI formats can use 256 QAM
enabled MCS/TBS table.
Besides when uplink 256 QAM is supported, the above options to
determine which table for CSI feedback can be applied to
determining whether to use 256 QAM uplink transmission as well. In
other words, either uplink 256 QAM implicitly determined when
downlink 256 QAM is configured, or a separate enabling
configuration can be considered. For uplink 256 QAM configuration,
different configuration per subframe set or per dynamic signaling
(depending on MCS) can be further considered.
When table can be changed via higher-layer signaling such as RRC,
it is necessary to consider RRC ambiguity issue. Initially, when a
UE is configured with periodic CSI reporting, aperiodic CSI
reporting, it is reasonable to assume that the indication of table
is included in the configuration of measurement reporting.
Similar to other parameters for CSI feedback, one option to change
CQI table is to reconfigure measurement parameters via RRC
connection reconfiguration messages. Since depending on the table,
CQI values are different, it could be also considered to change the
PUCCH resource for CSI feedback and then by decoding the PUCCH
resource and payload, eNB may be able to determine which table the
UE has used for CQI feedback.
A separate parameter also can be considered such as
"256QAMCqiTableUsed" where if this is true, 256 QAM table is used
and if this is not true, legacy table is used. When reconfiguration
of this parameter is occurred, indication or configuration of an
explicit PUCCH resource can be also considered. For example,
n.sub.PUCCH for PUCCH format 2 can be additionally configured (may
be separate for each p).
Another example of avoiding RRC ambiguity issue is to assign
additional "PUCCH" resource which will be used only in RRC
reconfiguration period for PUCCH format 2, 1a, 3 all together
potentially regardless of acknowledgement resource indicator (ARI)
or application resource optimizer (ARO).
In RRC reconfiguration period, PUCCH may be transmitted or only CQI
feedback will be transmitted in that additional resource to
eliminate the ambiguity.
Another possibility is to report both CQI values via TDM or FDM
approach. If TDM is used, for example, CQI report based on each
table can be reported in a round robin manner per each CQI
reporting instance. If FDM is used, for example, additional
resource (+1 from the original configuration) can be used to
transmit the second CQI.
Yet Another possibility is to create the table such that two tables
have common entries. For example, from two tables, the entries of
0-1, 5-15 are reserved as the same where 2-4 will be used for QPSK
in legacy table and for 256 QAM in 256 QAM table. In RRC
reconfiguration period, UE selects CQI only from 0-1, and 5-15 such
that there is no ambiguity in the network side. Or, the network may
assume common entries of CQI reports are valid and reports on
non-common entries may be dropped or ignored. If this is used, if
256 QAM is used, it may not be true that higher CQI value means
better channel condition as CQI entries for 256 QAM uses the low
indices such as 2-4.
Another option to handle RRC ambiguity is to ignore any CSI
feedback reported during RRC reconfiguration (in other words, it
does not matter which table the UE is using). In this case, to save
UE energy, a UE may drop CQI feedback during the RRC
reconfiguration period. Or, a UE may be configured with the
behaviour whether to drop CQI feedback during RRC reconfiguration
or not.
When CQI table design to consider RRC configuration is formulated
such that CQI index may not increase with spectral efficiency, we
discuss further how to report differential CQI.
Table 5 is another 4 bit CQI table for 256 QAM. In table 5, CQI
index may not increase with spectral efficiency.
TABLE-US-00005 TABLE 5 CQI index for differential CQI index
modulation code rate .times. 1024 efficiency CQI 0 out of range 0 1
QPSK 78 0.1523 1 2 256QAM xxx x.xxxx 16 3 QPSK 193 0.3770 3 4
256QAM xxx x.xxxx 17 5 QPSK 449 0.8770 5 6 256QAM xxx x.xxxx 18 7
16QAM 378 1.4766 7 8 16QAM 490 1.9141 8 9 16QAM 616 2.4063 9 10
64QAM 466 2.7305 10 11 64QAM 567 3.3223 11 12 64QAM 666 3.9023 12
13 64QAM 772 4.5234 13 14 64QAM 873 5.1152 14 15 64QAM 948 5.5547
15
In this case, we can have a mother CQI table for differential CQI.
Table 6 is a mother CQI table.
TABLE-US-00006 TABLE 6 CQI index for differential CQI modulation
code rate .times. 1024 efficiency 0 out of range 1 QPSK 78 0.1523 2
QPSK 120 0.2344 3 QPSK 193 0.3770 4 QPSK 308 0.6016 5 QPSK 449
0.8770 6 QPSK 602 1.1758 7 16QAM 378 1.4766 8 16QAM 490 1.9141 9
16QAM 616 2.4063 10 64QAM 466 2.7305 11 64QAM 567 3.3223 12 64QAM
666 3.9023 13 64QAM 772 4.5234 14 64QAM 873 5.1152 15 64QAM 948
5.5547 16 256QAM xxx x.xxxx 17 256QAM xxx x.xxxx 18 256QAM xxx
x.xxxx
The mother CQI table includes both legacy table and 256 QAM table
as following where differential CQI is mapped to CQI value from the
mother table.
For example, if wideband CQI reporting reports CQI=3, then the CQI
value would be determined CQI index from mother table+offset level,
e.g., offset level=1 means CQI=4 which maps to spectral efficiency
of 0.6016.
In RRC reconfiguration period, if wideband CQI value would be 2, 4,
6 (for example) which are used for 256 QAM, differential CQI values
could be ambiguous, and thus, values for those entries may not be
used in RRC ambiguity period. That is, the table used for wideband
CQI and sub-band CQI may be different where the common
entries/behaviors are preserved regardless of RRC
reconfiguration.
In other words, a mother table containing both legacy entries and
256 QAM entries can be specified where a table used as wideband CQI
table can be configured.
This approach offers some benefits as follows. (a) Since
differential CQI can address all CQI entries, those entries can be
used for determining proper MCS levels, especially for cell-common
data and data scheduled via CSS which may not use 256 QAM MCS
entries. (b) It offers an easy RRC reconfiguration as RRC ambiguity
issue would not be significant. (c) it offers to utilize DCI 1A for
compact DCI with 256 QAM; Yet, to support all the VoIP packet size
with flexible data rate and number of RB allocation, it would be
desirable to support DCI 1A via Common search space (CSS) with
legacy table (also DCI 1A with UE-specific search space (USS) can
be based on legacy table for this matter as well).
On the other hand, even though this approach may mitigate the RRC
ambiguity issue, still, some entries are not usable at RRC
reconfiguration where VoIP traffic may be affected as DCI 1A with
those MCS entries are not schedulable in RRC reconfiguration via
USS.
As CSS offers only high aggregation levels (AL) (4/8), it may not
be so efficient operation if RRC reconfiguration is frequent. Thus,
regardless of this approach, using legacy table with DCI 1A should
still be considered depending on the frequency of DCI 1A scheduling
and full supportability on VoIP data rates. Also, this approach
requires UE to perform CQI calculation using two different tables
and adds burden on eNB to infer differential CQI values.
Even though a new table for differential CQI, as an example
described in this disclosure, is designed assuming CQI table for
wideband has "out-of-order" CQI indices not aligned with spectral
efficiency, the new table approach for differential CQI can be
applied regardless of CQI table used for wideband.
For example, wideband CQI table is formulated similar to, the
differential CQI table can be formulated such as where differential
CQI is calculated using the differential CQI table where the
mapping between wideband CQI and the reference CQI index in
differential CQI table is as Table 7.
TABLE-US-00007 TABLE 7 CQI index for differential Wideband CQI
modulation code rate .times. 1024 efficiency CQI index 0 out of
range 0 1 QPSK 78 0.1523 1 2 QPSK 120 0.2344 3 QPSK 193 0.3770 2 4
QPSK 308 0.6016 5 QPSK 449 0.8770 3 6 QPSK 602 1.1758 7 16QAM 378
1.4766 4 8 16QAM 490 1.9141 5 9 16QAM 616 2.4063 6 10 64QAM 466
2.7305 7 11 64QAM 567 3.3223 8 12 64QAM 666 3.9023 9 13 64QAM 772
4.5234 10 14 64QAM 873 5.1152 11 15 64QAM 948 5.5547 12 16 256QAM
xxx x.xxxx 13 17 256QAM xxx x.xxxx 14 18 256QAM xxx x.xxxx 15
For example, referring to Table 7, if wideband CQI is reported as
2, then the differential CQI value of -1 would be mapped to
spectral efficiency of "0.2344" which is CQI index 2 in
differential CQI table.
In principle, two tables for wideband CQI and differential CQI can
be different. Thus, wideband CQI may not be able to refer all the
spectral efficiency values however differential CQI can refer to
those entries removed from wideband CQI table when 256 QAM is
configured.
Alternatively, a table can be considered which includes entries
covering spectral efficiency from xx % to yy % with equal steps (or
potentially different for 256 QAM entries where the same step size
is used among 256 QAM entries), then a table used for wideband CQI
reporting can be higher layer configured or predetermined.
In terms of reporting wide-band CQI, the index values can be chosen
from the selected indices only whereas the differential CQI and
other measurement can use the table with all the entries. In this
case, depending on UE SINR condition, which entries will be used
can be higher-layer configured.
Next, the table change can be done via Medium Access Control (MAC)
control element (CE). To potentially reduce the RRC ambiguity
period and make the fast transition between tables, MAC control
element based (similar to SCell activation/deactivation) approach
can be also considered. If this is used, the effective timing of
the new table configured via MAC CE follows the same timing of MAC
CE for SCell activation (i.e., n+8). If CQI occurs before n+8 when
MAC CE has been received at subframe n, it uses the previous CQI
table, or it may drop CQI. Simply, the network may ignore any CQI
feedback reported before A/N is received for MAC CE command once
table change command is triggered via MAC CE.
Finally, the table change can be done via physical layer signalling
such as DCI such as aperiodic CSI request or NDI or new DCI or etc.
Another possible approach is to dynamically change the table via
DCI indication.
For example, if aperiodic CSI request can include the indication of
which table to be used for a given CC, once aperiodic CSI request
is triggered, the UE may assume that the table is switched to the
table indicated by the aperiodic request. Another example would be
that CSI request can be triggered with zero resource allocation,
then it may be assumed as a command to change the table (i.e.,
toggle between two table. In other words, if the UE has used 256
QAM table, it changes to legacy table and vice versa). Or, downlink
DCI can be also used to trigger table switch (such as DCI 1A with
zero resource allocation similar to SPS activation DCI).
To determine which table is more suitable, occasionally, the
network may request CQI values on both tables. One approach is to
transmit CQI calculated from both tables by aperiodic CSI feedback
when aperiodic CSI request is triggered for a UE which is
configured to use 256 QAM. Instead of transmitting one CQI per CSI
process for a component carrier (CC), if a UE is configured with
256 QAM, it will report CQI values calculated based on both tables
(256 QAM and legacy CQI tables). Based on CQI feedback, the network
may be able to determine which table is more appropriate and then
reconfigure the table.
So far, we have looked at different approaches of changing tables
between legacy and 256 QAM CQI tables. Given that operating SINR
range may change dynamically and also the change can occur any
time, table change could occur frequently. Accordingly,
reconfiguration may not be desirable.
Thus, we consider cases where reconfiguration is not assumed. In
this case, some special handlings would be necessary to address the
diverse range of SINR. One example is to configure two CSI process
for the same CC even without CoMP configured where one CSI report
is based on legacy CQI table whereas the other is based on 256 QAM
table. In this case, PMI-RI may not be configured for the second
CSI process separately as PMI and RI values could be the same.
In other words, regardless of PMI-RI configuration of the first
CSI, the second CSI process may not report any PMI or RI. It will
report only CQI following the period configured for the CSI
process.
A separate CSI configuration can be given to the second CSI
process. If the currently configured table is appropriate (i.e.,
operating SINR range is good for the configured table), then the
second CSI may not be necessary to be reported. In that case, CQI
feedback will be reported only for the second CSI process period.
In other words, when two CSI processes are configured, PMI and RI
are reported following the first CSI process configuration.
For CQI report, it may be selected based on the condition of SINR.
The UE may report only one CQI based on the proper CQI table based
on UE measurement. For example, a UE experiences relatively low
SINR, it may use the legacy CQI table and report the CQI in the
resource configured for the second CSI process (if legacy CQI table
is configured for the second CSI process) and it may not transmit
CQI at the resources/subframes configured for the first CSI process
(since 256 QAM table is configured for the second process).
For the second CSI process, it may be assumed that other parameters
are the same to the first CSI process unless it is configured
otherwise. The network may detect the correct value by receiving
CQI report and also the resource location.
Another approach is to use CSI measurement sets where each set is
associated with one table. Drawbacks of these approaches would be
that it would not be easy to combine with CoMP operation or ICIC
techniques.
Yet another approach is to define a new reporting type which can
use 256 QAM table where CQI with current reporting type is
calculated based on legacy table whereas new reporting type reports
wideband CQI (or subband CQI as well) based on 256 QAM table. Or, a
higher layer configuration to use which table for each reporting
type can also be considered.
Lastly, if 256 QAM table is configured mainly for sub-band,
wide-band CQI can be reported using legacy table whereas
differential CQI can be reported using the 256 QAM enabled where
the differential CQI can be mapped in a 256 QAM enabled table.
For example, if is used for wideband CQI reporting where is used
for differential CQI computation, if CQI index=3 (mapped to
spectral efficiency of 0.3770) is reported with differential CQI=-1
which corresponds to CQI index=2 in (mapped to spectral efficiency
of 0.8770). In this case, spectral efficiency has been
increased.
This approach has some drawbacks and advantages. Some CQI entries
(particularly in low SINR) may not be addressable by differential
CQI reporting due to the limited offset values which may be more
important in differential CQI feedbacks whereas higher SINR (256
QAM operating SINR range) can have benefits from this approach.
FIG. 5 is a flow chart for describing an operation of UE and eNB
according to the invention(s) in this disclosure.
Referring to FIG. 5, the eNB may transmit reference signals and the
UE may receive reference signals on the downlink channels
(S510).
The UE may configure CSI based on the received reference signals
(S520). The UE may perform a measurement for channel state with the
reference signals. The UE may select CQI index on a CQI table
according to the channel state. The CQI index may specify
modulation scheme, code rate, efficiency, etc. on the CQI
table.
The UE and the eNB may use two CQI tables to use 256 QAM according
to the invention(s) of this disclosure. For example, CQI table for
legacy CQI and CQI table for using 256 QAM can be used.
The CQI table for legacy CQI may map CQI index into one of QPSK, 16
QAM, and 64 QAM and the CQI table for using 256 QAM may map CQI
index into one of QPSK, 16 QAM, 64 QAM and 256 QAM. The eNB may
transmit signals for indicating which CQI table is used. The signal
may be transmitted by a RRC signalling or by DCI. Or the CQI to be
used can be determined by MAC CE.
In addition, the UE and the eNB may also use a legacy CQI table and
mother CQI table. The mother CQI table may be configured with
entries of legacy CQI table and entries for 256 QAM. Thus, the
legacy CQI table may be configured with 4 bits and the mother CQI
table may be configured with more than 4 bits, for example 5 bits,
etc. The mother CQI table, the legacy table and their CQI indices
are described in detail above.
The UE may report CSI including CQI on the uplink channel (S530).
The eNB may specify the downlink channel state with the received
CSI and may decide modulation scheme according to the CSI. The eNB
may specify downlink channel quality using CQI index in the CSI.
The eNB may use same CQI table which the UE used.
FIG. 6 is a block diagram which briefly describes a wireless
communication system including a UE 600 and a BS (eNB) 640. The UE
600 and the BS 640 may operate based on the described as
before.
In view of downlink, a transmitter may be a part of the BS 640 and
a receiver may be a part of the UE 600. In view of uplink, a
transmitter may be a part of the UE 600 and a receiver may be a
part of the BS 640.
Referring to FIG. 6, the UE 600 may include a processor 610, a
memory 620, and a radio frequency (RF) unit 630.
The processor 610 may be configured to implement proposed
procedures and/or method described in this disclosure. For example,
the processor 610 may configure CSI comprising CQI index using
reference signals.
The processor 610 may perform measurement on channel state based on
the reference signal and may select CQI index corresponding
measured channel state on the CQI table. The processor 610 may use
two CQI tables. For example, the processor 610 can use CQI table
for legacy CQI and CQI table for using 256 QAM. The CQI table for
legacy CQI may map CQI index into one of QPSK, 16 QAM, and 64 QAM
and the CQI table for using 256 QAM may map CQI index into one of
QPSK, 16 QAM, 64 QAM and 256 QAM. Which table to be used is
signalled or determined using predetermined method.
For another example, the processor 610 can also use a legacy CQI
table and mother CQI table. The mother CQI table may be configured
with entries of legacy CQI table and entries for 256 QAM. Thus, the
legacy CQI table may be configured with 4 bits and the mother CQI
table may be configured with more than 4 bits, for example 5 bits,
etc.
The CQI tables, CQI indices and method to choose CQI table to be
used are same as described as before.
The memory 620 is coupled with the processor 610 and stores a
variety of information to operate the processor 610 such as CQI
tables. The RF unit 630 may also coupled with the processor 610.
The RF unit 630 may receive reference signal and transmit CSI.
The BS 640 may include processor 650, a memory 660, and a RF unit
670. Here, the BS 640 may be PCell or SCell and the BS 640 may be a
macro cell or small cell. In addition the BS may be a source cell
for network synchronization or a target cell for network
synchronization.
The processor 650 may be configured to implement proposed procedure
and/or method described in this disclosure. For example, the
processor 650 may transmit reference signal on downlink channel.
The processor 650 may specify the downlink channel state with the
received CSI and may decide modulation scheme according to the CSI.
The processor 650 may specify downlink channel quality using CQI
index in the CSI. Here, the processor 650 may use same CQI table
used in the UE 600.
The CQI tables, CQI indices and method to choose CQI table to be
used are same as described as before.
The memory 660 is coupled with the processor 650 and stores a
variety of information to operate the processor 650 such as CQI
tables. The RF unit 670 may also coupled with the processor 650.
The RF unit 670 may transmit reference signal and receive CSI.
In the above exemplary systems, although the methods have been
described on the basis of the flowcharts using a series of the
steps or blocks, the present invention is not limited to the
sequence of the steps, and some of the steps may be performed at
different sequences from the remaining steps or may be performed
simultaneously with the remaining steps.
Furthermore, the above-described embodiments include various
aspects of examples. Accordingly, the present invention should be
construed to include all other alternations, modifications, and
changes which fall within the scope of the claims.
In the description regarding the present invention, when it is said
that one element is "connected" or "coupled" to the other element,
the one element may be directly connected or coupled to the other
element, but it should be understood that a third element may exist
between the two elements. In contrast, when it is said that one
element is "directly connected" or "directly coupled" to the other
element, it should be understood that a third element does not
exist between the two elements.
* * * * *